For example, in a school of a country that does not give opportunity to its people, where most of the students are poor, it is unlikely that the teachers will induce them to think big or have big dreams...more likely they will aim to keep them apart from drugs, avoid problems with the government and try to imbue some basic skill for life. The ultra-poor do not even get that - which actually may be better.
Just for the fact that we don't live in a classless society, people are bound to have better opportunities/stand better chances of success than others even right from birth, even ones country of birth other than the immediate family plays a part in that, it's much better to be born in a developed country than an underdeveloped one, but even having said that, it doesn't mean than if one is privileged to have such advantages that they outrightly will be better than those who are not, of course their chances are higher, but they still have work to do on their own path, thus even people from poor backgrounds/underprivileged countries still break the chain and achieve success, hardwork has a lot to play in success, though a good background makes things a whole lot easier.